The field of the present invention relates to optical scanning systems and particularly to an aiming system for use with an optical scanning system. The invention is especially suitable for use in a laser scanner for reading bar codes such as those found on consumer products, most frequently the UPC bar code. The invention is particularly suitable for handheld scanners.
Bar code scanners, as any optical system, require an outgoing scan beam to be properly drawn over the intended target such as the bar code. A problem arises where laser scanners, in particular handheld scanners, are used to scan bar code labels located a great distance from the laser scanner. Over distances of several feet, scan lines become so diffuse that they are not readily visible on a target, making it difficult for the operator to properly aim the scanner at the target or effectively manipulate the target to be read. This difficulty arises because the path of the beam across the surface carrying the bar code label may not be readily visible to the operator of the scanner due to the high speed of movement of the beam tracing the scan line or due to low intensity of the visible scan line. Thus, for example, it has been found that targeting and reading a bar code 3 inches by 1 inch in size at a distance of five feet becomes problematic.
In response to this problem, laser scanners have been developed having a two-position trigger which causes the laser scanner to generate either a scan line or a fixed pointer beam for aiming the laser scanner. For example U.S. Pat. No. 4,760,248 discloses a portable laser diode scanner equipped with a trigger-actuated aiming light for visually locating and tracking the symbol. The pointer beam or aiming light is visible over a greater distance, because the light energy is concentrated in a spot. However, trigger-actuated aiming lights and two-position scanners have the disadvantage of requiring manual switching of the scanner between operating modes and, once switched from the pointing mode back to the scanning mode, they again leave the operator "blind" to the direction in which the scanner is pointed while scanning.
Accordingly, improved performance and targeting capability are desired to satisfy the continuing need for high performance scanners for use in a wide range of applications.